The present invention relates to wireless communication, but more specifically to a method of determining RF coverage area in a point-to-multipoint RF transmission system.
In traditional wire-line telephone networks, subscriber telephones are connected to a central office (CO) switching facility via central office trunks (i.e., local telephone lines). Multiple switching facilities located throughout a given region communicate with each other and, in turn, interconnect subscribers through various communities. Fixed wireless systems, on the other hand, use radio frequency (RF) links that replace traditional wire line interconnections between switching facilities and subscriber telephones. As shown in FIG. 1, a typical fixed wireless system includes at least one mobile switching center (MSC) 110 that provides a gateway to a wire-line public switched telephone network (PSTN) 120. The system also includes remote stations 130 that are used by mobile subscribers 140, 141 or wired subscribers 150, and at least one base station 160 that is linked with the switching center and several remote stations. Each remote station may communicate with the base stations on different frequencies. Unlike traditional wireless communication systems, the remote stations in a fixed wireless system may be configured to communicate with only one specific base station.
Determination or prediction of RF coverage area provided by a base station plays an important role in the installation and servicing of fixed, remote stations at customer premise locations. RF coverage generally refers to the geographic area in which a remote station 130 may effectively communicate with a base station 160 without significant signal interruption or degradation. Prior to installing a remote terminal or station at a customer premise location, it is initially determined whether base station RF signals received at a customer's location meet required signal strengths for suitable service. High accuracy in coverage area prediction obviates needless dispatching of installation and maintenance crews to a customer premise location that lies outside an effective RF coverage area of a base station, and therefore assures successful and cost-efficient operations.
Mathematical models, such as the Cost 231/HATA method, are conventionally used to predict whether a site located at a particular address is serviceable by a fixed wireless system. Mathematical models, however, vary in degree of sophistication and accuracy, and many of them previously used have several drawbacks. A first drawback is the susceptibility of inaccuracy due to changes in environmental conditions. Another concerns the expense of replicating, if at all possible, the morphology, land usage types, physical structures and terrain combinations found in regions to be studied. Accordingly, mathematical models used in the past are only capable of predicting accurately up to about 70%.
Therefore, an object of the present invention is to provide a method of accurately predicting RF coverage area in point-to-multipoint wireless systems so as to enable strategic decision-making and/or planning relative to providing, installing, or maintaining a point-to-multipoint wireless transmission system.